Apparatus and method for the electronic representation of characters



Sept. 8, 1959 E. HOFFMANN 2,903,615

I APPARATUS AND METHOD FOR THE ELECTRONIC REPRESENTATION OF CHARACTERS Filed June 5, 1957 ravy APPARATUS AND METHOD FOR THE ELEC- T IEESNIC REPRESENTATION OF CHARAC Application June 3, 1957, Serial No. 663,296

f niteci States Patent Claims priority, application Germany November 13, 1956 A 6 Claims. (Cl. 315-85) The present invention relates to apparatus and a method for the electronic representation of characters, particularly digits, on the screen of cathode ray tubes in connection with which means known per se serve inter alia advantageously for the partial darkness control.

It is already known to represent characters such as letters and numbers electronically. In this connection use is made of the Lissajou and other figures or curves which can be produced in a known manner, certain parts of these curves being made invisible by darkness control (see article An Electronic Alphabet Generator by G. T. Clack in Electronic Engineering, May 1948). The means required for this type of representation of characters are, in addition to vacuum tube generators for the formation of the starting'curves, still other vacuum tube generators for the production of the darkness control pulses.' 'While such apparatus make it possible to form all letters, this is only conditionally possible in the case of numbers. In this connection, thesearrangements require both a relatively large technical expenditure and a relatively large power expenditure, for instance for tube heating. In this connection the invention would be of particular advantage for instance if it weredesired to apply this typeof representation of characters, particularly numbers, in the announcing of train numbers in railway safety installations to the extent necessary in the field. Furthermore, however, electron tubes are by themselves disadvantageous in railway safety installations for the reason that the burning out of a filament as well as a decrease in the emission constitute factors of uncertainty which cannot be tolerated.

Furthermore, it is readily imaginable that due to a decrease in the power of the tubes there are produced darkness control pulses which permit either no darkness control or an unintended darkness control, and thus permit the production of either no clear character or of an incorrect character. The object of the present invention, therefore, is to avoid the abovementioned defects as far as possible.

In accordance with the invention this is done by means known per se, for instance rectifiers, which selectively vary the curve of the Lissajou figure and cause the control grid of the cathode ray tube to be acted upon by voltages the form and amplitude of which are caused by rectified sine voltages and/or sine voltages distorted by means of a supersaturated iron core, of 50 cycles or frequency-double 50 cycles (100 cycles) and the phase position of which is caused by an R-C member which is simultaneously employed.

The advantages obtained by the invention reside essentially in the fact that due to the elimination of vacuum tube generators for the purpose both of forming the output cathode ray tube figure to be selectively modified and also for the purpose of forming dark control impulses, considerable savings in power are obtained. Furthermore, the technical complexity is reduced to a minimum. A particularly great advantage, however, is that the apparatus of the invention has practically no susceptibility to disturbance so that there is obtained an increase in the dependability in operation of installations embodying the invention, and particularly installations for train number indication which would not be achieved with the means previously used.

The subject matter of the invention will be explained in further detail in connection with the drawings wherein:

Fig. 1 is a diagram of a cathode ray tube circuit;

Fig. 1a is a diagram of a circuit for producing deflection voltages;

Fig. 1b is a diagram for producing blanking voltages;

Figs. 2a to 2e illustrate the transformation of a Lissajou figure into a numerical digit.

KS is the cathode ray tube or indicating tube which is equipped with a cathode K, control grid G, focusing anode 11 and anode 12, and with pairs of horizontal and vertical deflecting plates h and v, respectively. Voltages are supplied to the electrodes of the tube by any suitable high voltage D.C. circuit 10 which may include resistors R9 to R13. l i

To terminals h and v of the cathode ray tube there are applied selected voltages for the formation of the starting figure, which voltages are taken from the switching arrangement of Fig. 1a. In this connection the voltages l to 3 (Fig. la) are applied selectively to the terminal v of tube KS and the voltages 4 and 5 to the terminal h. By the application of a voltage having a frequency of 50 cycles between terminals 13 and 14, and that of cycles between terminals 14 and 15, a Lissajou figure is produced in the known manner, the form of which figure can still be changed by the entire or partial reduction of positive or negative half-waves. For this purpose there are employed variable. resistors R1 or. R2 which are connected in parallel to suitably connected .rectifiers G11 and G12. The rectifier'GlS for thefrequency of 100 cycles is not provided with a variable resistance, since in this case entire half-waves are blocked. A leakage path from terminals 2, 3 and 4 to ground is provided by resistors R6, R7 and R8. 1 The circuit arrangement shown in Fig. 1b serves for the darkness control of certainpartsof vthe above described curve. In this circuit SO'an'd 100 cycle voltages are supplied through transformers Tr1 and T12. Voltages which are taken from the switch arrangement in accordance with Fig. lb arbitrarily at terminals 6, 8 and 9, respectively, are applied to terminal G of tube KS by a suitable selector switch 20. The terminal 7 is in each case connected with terminal K of the tube. The voltages at terminals 6, 8 and 9 which differ in form and frequency are superimposed on the negative grid bias so that, depending on the phase position of the superimposed voltages, the aforementioned parts of the starting curve train are controlled in darkness. The elements R3C3 and RS-CS serve to produce the desired phase position of voltages of 50 and 100 cycles, respectively. The transformer Tr, the core of which is oversaturated, supplies particularly short pulses, depending on the degree of saturation. This action, however, can also be obtained by glow tubes.

If it is desired, for instance, to represent the digit 5 in accordance with Fig. 2, the following three different voltages are applied to tube KS:

(a) To the vertical pair of deflecting plates v, the voltage of terminal 3 (Fig. la),

(b) To the horizontal pair of deflecting plates, the voltage of terminal 4 (Fig. la),

(c) To the control grid the voltage of terminal 8 (Fig. 1b).

In Figs. 2a to 22 it is shown how the above-mentioned connections act.

The figure shown in Fig. 2a is produced by deflection of the cathode ray with pure sine voltages in the frequency ratito of 1:2. From this figure by replacement of one pure sine voltage by the voltage of terminal 3 (Fig. la), there is produced the figure shown in Fig. 2b. From this by further replacement of the other pure sine voltage by the voltage of terminal 4- (Fig. 11)), there is produced the figure shown in Fig. 2c. The dotted line portion of Fig. 2d is that part of Fig. 20 which remains invisible due to the application of darkness control. This is achieved by applying the voltage of terminal 8 (Fig. 1b) to the control grid G of tube KS.

In order to obtain the number 4 from a Lissajou figure, the following voltages are applied to the deflecting plates:

(a) Horizontal deflection voltage from terminal 4 of the circuit of Fig. 1a and terminal 8 of Fig. 1b are applied together to the horizontal deflection plate terminal h, the supply voltages being at a frequency of 100 cycles per second. The phase relation of the two voltages at terminals 4 and 8 is such that the positive half sine wave at terminal 4 is between zero degrees and 180 degrees and the negative impulse at terminal 8 is between 180 degrees and 270 degrees. Between 270 degrees and 360 degrees the amplitude is zero volts.

(b) Vertical deflection is effected by the partially rectified sine voltage which is taken off at terminal 3, Fig. la. The resultant flattened portion of the half wave at terminal 3 corresponds to the portion of the wave between 90 degrees and 270 degrees of the horizontal 100 cycle deflection voltage. In this way the phase of the two deflection voltages relative to each other is unambiguously defined.

(c) Blanking control is effected by a voltage taken off terminal 6 of Fig. 1b. The phase relation of this voltage is selected so that the tube is blanked at the time that the negative halfwave of the vertical deflection voltage is effective.

The digits 1 to 9 can be formed. Digit is formed by two sine voltages of different amplitudes and the same frequency, displaced 90 in phase from each other. In this connection the size of the digits shown is dependent in known manner on the value of the deflecting amplitudes. The voltages may be applied to terminals K, G, h and v of tube KS by selector switches 19 and 20 operated in unison.

I have described what I believe to be the best embodiments of my invention. I do not wish, however, to be confined to the embodiments shown, but what I desire to cover by Letters Patent is set forth in the appended claims.

1. A method of changing Lissajou figures to form numenical digits on the screen of a cathode ray tube which comprises producing and selectively applying portions of a rectified or an unrectified sinusoidal voltage of one frequency to one pair of deflecting plates and of twice that frequency to the other pair of deflecting plates and blanking the electron beam during selected portions of each cycle thereof.

2. A circuit arrangement for producing numerical digits comprising a cathode ray tube having pairs of horizontal and vertical deflection plates, means for producing rectified and unrectified portions of sinusoidal voltages of a first frequency, means for producing rectified and unrectified portions of sinusoidal voltages of a sec ond frequency which is twice said first frequency, means for selectively applying said voltage portions to the horizontal and vertical deflection plates, and means for blanking the electron beam of said tube during selected portions of each cycle thereof, said last means comprising means for producing a plurality of voltages having different phase relations with respect to said sinusoidal voltages, and means for selectively impressing said plurality of voltages between the control grid and cathode of said cathode ray tube.

3. A circuit arrangement according to claim 2, wherein the means for producing rectified voltages of said first frequency include first and second rectifiers and variable resistors in parallel with each of said rectifiers.

4. A circuit arrangement according to claim 3, wherein said rectifiers are oppositely poled.

5. A circuit arrangement according to claim 2, wherein the means for producing the blanking voltages includes a transformer having a magnetic core, and means for saturating said core.

6. A circuit arrangement according to claim 2, wherein the means for producing the blanking voltages comprises means including a glow tube for producing short voltage pulses.

References Cited in the file of this patent UNITED STATES PATENTS 

